1. Field of the Invention
This invention relates to a cover unit for closing the roof opening in the solid skin of a motor vehicle roof. The cover unit comprises a cover element of an at least partially transparent plastic and a reinforcing frame, made of metal, which extends along the side edge of the cover element. The reinforcing frame also bears a seal which surrounds the side edge of the cover element for contact against an essentially vertically running roof-mounted sealing surface.
2. Description of Related Art
Due to their low weight and a fracture resistance, which is greater than that of glass covers, as well as the high degree of design freedom provided, plastic cover units are enjoying increasing popularity in motor vehicle construction. These advantages are offset however by the fact that the plastics conventionally used have a coefficient of thermal expansion which is much higher than that of metal, which can be a problem at the fluctuating temperatures to which vehicles are ordinarily exposed.
A conventional cover unit of this type is described in International Patent Application Publication WO 97/03855. The cover unit of WO 97/03855 has near the edge of the cover element a plurality of pins which are molded integrally to the bottom of the cover element. The reinforcing frame, which is located likewise on the bottom of the cover element, has slotted guide channels for receiving the pins. The slots all lay on the lines which run through the center of gravity of the cover element. A seal is also attached to the edge area of the reinforcing frame. This cover element has two disadvantages. Initially, it is noted that the cover unit is expensive to produce and install due to the plurality of pin connections to be molded on and then mounted. Secondly, the thermal expansion of the cover element increases the contact pressure of the seal against the roof frame; this can lead to sticking of the cover to the roof.
A similar cover unit is described in published German Patent Application DE 198 33 934 A1. In the motor vehicle window device shown in DE 198 33 934 A1, a plurality of holding devices, to which a reinforcing frame is screwed, are molded to the bottom of the plastic cover. In order to permit relative motion between the cover element and the reinforcing frame, upon thermal expansion of the cover element, holes having a diameter clearly greater than the diameter of the screws are formed in the holding devices. To prevent the screws from falling through overly large holes additional shims are placed on the screws. The cover element known from DE 198 33 934 A1 also requires complex, costly, and time-consuming production methods. Further, if all the screws are not equally tightened, and upon repeated expansion and contraction of the cover element, misalignment of the cover unit with respect to the roof frame occurs such that the cover unit gets stuck.
Another cover element is disclosed in German Patent DE 30 41 505 C2 where a rigid cover unit of the type mentioned above is disclosed in which the cover element is bordered by the reinforcing frame. Since the reinforcing frame in DE 30 41 505 C2, when under the influence of temperature, opposes the thermal expansion of the cover element, then twisting and unwanted warping of the cover element can occur.
In view of the problems which are inherent in the known cover units, it is an object of this invention to devise a cover unit of the type mentioned above which can be produced and installed more easily and more economically. Furthermore, the cover unit will enable construction of a vehicle roof having a so-called flush design, i.e., a roof in which the cover element and the seal are level to one another and the seal is not distorted upward out of the roof plane under the influence of the cover element, particularly during thermal expansion of the cover element. Expansion of the seal out of the roof plane can lead to unwanted wind noise.
This object is achieved by a cover unit in which the reinforcing frame is cemented to the cover element. The cementing is carried out using a flexible cement which enables the cover element to move in the transverse direction relative to the reinforcing frame in order to enable thermal expansion of the cover element. The result is that the seal has a roof sealing area which is substantially unaffected by thermal expansion of the cover element when in contact with the roof-mounted sealing surface, and that a cover sealing area for compensation of thermal expansion of the cover element is provided. Preparation of a roof sealing area which is substantially unaffected by thermal expansion of the cover element prevents warping of the seal provided between the cover element and the roof frame. The flexible adhesive connection between the reinforcing frame and the cover element also permits a certain amount of motion of the cover element relative to the reinforcing frame such that warping of the cover element is also inherently prevented. In order to ensure the sealing action between the cover element and the fixed roof surface, even during varying expansion of the cover element, a cover sealing area is provided which accommodates or compensates for the thermal expansion of the cover element.
In particular, the reinforcing frame has an edge area which runs essentially parallel to the side edge of the cover element and forms a contact surface both for the roof sealing area and also for the cover sealing area, and the edge area of the reinforcing frame encompasses a surface area which extends essentially vertically.
The seal can be slipped onto the edge area of the reinforcing frame or onto a seal carrier which is separately molded on the reinforcing frame. Then, the seal can contain a reinforcing insert, made of steel for example, in order to preserve the shape of the seal especially when it is slipped onto the edge area which thus prevents unwanted loosening of the seal from the reinforcing frame. However, the seal can also be cemented or locked to the reinforcing frame or joined in some other way.
Compensation for the thermal expansion of the cover element by means of the cover sealing area can be accomplished in several ways. According to one preferred embodiment, the cover sealing area and the part of the cover element which interacts with it are configured and arranged such that the cover element can also slide on the cover sealing area when the effects of temperature on the cover sealing area causes contraction or expansion of the cover element.
The cover sealing area and the part of the cover element which interacts with it can be configured and arranged by suitable shaping such that sliding motion of the cover element relative to the cover sealing area causes essentially no deformation of the cover sealing area. For example, this can be done by the cover sealing area and the cover element interacting along an engagement surface which extends essentially parallel to the direction of the relative motion of the cover element relative to the reinforcing frame caused by the effect of temperature. To facilitate the motion of the engagement surfaces against one another, there can also provided a lubricating varnish in the contact area between the cover sealing area and the cover element.
The arrangement can also be made such that the cover sealing area can be elastically deformed for compensation of the thermal expansion of the cover element.
When a flush design is desired, the visible top of the seal and the top of at least the area of the cover element adjacent to the seal are structured to extend essentially in a coplanar manner. Additionally, provisions can be made for the side edge of the cover element to fit over the elastic part of the cover sealing area such that when thermal expansion of the cover element occurs the elastic part of the cover sealing area dips under the side edge of the cover element.
Depending on the space required to accommodate the individual components and depending on the stiffness to be provided by the reinforcing frame, the edge area of the reinforcing frame can encompass a lowered area in which the cover sealing area is located.
Preferred embodiments of the invention are explained below with reference to the accompanying drawings.